Pressure regulating apparatus for cutting and welding torches and the like



Feb. 22, 1955 R R L GEFFROY 2,702,561

PRESSURE REGULA'ING APPARATUS FOR CUTTING AND WELDING TORCHES AND THE LIKE Filed May 2l. 1949 3 Sheets-Sheet l Feb. 22, 1955 R R GEFFROY 2,702,561

PRESSURE REGULATING APPARATUS FOR CUTTING AND WELDING TORCHES AND THE LIKE Filed May 21, 1949 3 Sheets-Sheet 2 JNVENTOR. /hf/ fief/ray TTURNEY Feb. 22, 1955 R. R. l.. GEFFROY PRESSURE REGULATING APPARATUS FOR CUTTING AND WELDING ToRcHEs AND THE LIKE Filed May 2l, 1949 5 Sheets-Sheet 3 United States wPatenti listan Resa-rassegna, Nearly-Sarsina sans Application May 21, 1949, Serial No. 94,704 Claims priority, applitioniFrance May 27, 1948 4 claras. (ci. 'E1-sist inv'e'n on" elates to pressureregulating apparatus and particlrl. .t'ppfatulfat Contrllins, the Pressure o f oxygen` a 1 1d/or fuel supplied to welding or cutting itorc'liesor' thelile. V.Oxygen isC'OmfrO uppledto torches.. Qf. thats/pe described from indi ual tanks .whos`e pressure when illedis in tlie'neighborlitjod of 150 lgL/jcm?. It'is icom- ;mon practice to use oxy'ge'n'frornjsuch Va tank vruntil its pressure drops toapproxirnately lig/cm?. One` type -ofconv'entional p ress'tireV regulator commonly used to ,Plv a. trch frfri' '8111.611 @..tanls iS. a tw'O-:Sa'safgulatort The tirststage reduces they pressure approxitely 40, ksQ/cm, ,andthe Se'csidA .Staseredusfthe pressure to whatever operating prefss'ureuifs selected by the operator of theftorch, vIn such systems, a wide fange of .Wrkine 'pressures' .isalsed inthe' fQrCh- The wrkins presure i`S.S.ltd `by .the jchf oprratrby the SCCOD rac'f- ,.Ifgrhinessure varies from the selected value, the operator i s inforu ied of 'the variationbl gag, and lie can always adjust 'c ausfethe rangeof'pres'surey l1 literate of iliw in suchv previous regu rs 1s o great.

In my copendingpmicnbn sefi'si'No; statin, ined February y23, 1946, entitled, Oxy/acetylene Installations .for, .Welding Cutting or theV L ik e, new Patent No. 2,533,729 dated December' 1 2), 195o, which isgfas s to the assignee of the presentapplication, .I haveI disc'losed an roxygen 'listributi'ng system, ingwliich oxygen is :Supplied at a constant pressure to several we 1ding or cutting torches, andin which rthe pressure regulatingapparatus, is effective to insure that the, pressure and` t1 e rate of flow 4tofeach torch are net aiected byI variatons in the rateof flow to the other torches.

V An object of the presentinventionis to providean improved pressure regulator for apparatus of the type described., which. is, .capable of, maintaining@ vSubstantially fixed outlet pressure over a` wide range of variation of the rateofow,

Anotherobject is to provide an improved oxygen and/ or fuel gas distributing system ofthe type ,described in* my copending application Serialk No. `649,704, now Patent No. 2,5 33,729 previously mentioned.

A further object is to'provideyingsucha system, improved means for preventing the backward Vliow ofl oxygen or fuel gas from one'torch to another.

A further object is to improve such-.a system by 'sirnplication of the pressure 'regulating and ow' controlling apparatus therein.

In accordance with the present' invention, a" y'n s'tja'r'it pressure `regulator "suitablt. for usein a system f the ty'p'e described in my' `copeidin'g-Y application' Serial N.

2,702,561 Patented Feb. 22, i955 ICC 2. 94H03, is provided by suitably modifyinga two-stage regulator of conventional construction. The modifications include: (1)1 adius. entof. the rsilstae'e 0f `the regulator totake the greater part of the pii'sure drop in th'e'lirst stage; 2) careful control of the relationship bet een the areapf the diaphragmandthe areaof the valve". in the second stag`efo f t le regulator; and\( 3) the provision of ineansforsealing' the'adjustment'of the sec- "ondjreg'ulatorstag'e s that it cannot be'changed byunauregulating both the fuel .One slave pilot valveis connected in a fuel gas bleed line and controls the pressure in a portion thereof. This controlled fuel 'gaspressure isusedto control the main oxygen pressure regulator. The other slave pilot valve controls the pressure in an oxygen bleed line, which controlled oxygen pressure is utilized to control the main fuel gas regulator. By virtue of this arrangement, main- Ie'nan oi both. the' enigen ad ,fuel gas` Supply pressures 'f iiued operation of bothtbemainregsupply pressure fails, the other main In fh] ,System J'fSt de" ribe, .th iliastejplt valve., is so coristrrred that it 1ny' e r`se ly compensates the regulated 'press je for' `variations in the iletpres'sureuffhat is', av decre e in the inlet pressure causes aninrease in d pressure.; This characteristic is utilized to penste fo"r' variations-in-the pressure dropthrough the lines connecting the pressureregulator to the torch. This compensation insures a constant pressure supply to fhe.t0rch,.reg1ird1e$$'f varitinsn the' supply pressure- In accordanc`e-with'- another modication of the presefit ihVIiC. ,hrh is PIQ/iddf with @dual rgultor. Whichcfrols Both the. fuel 'and xyse'llipessures attlie torch. .Th `d1 1al regulator is controlled bythe pressure .i111 a vBleed lin Qifd, t0 the `Oxygen 4Supply and regulated by a` `s`lave p ilot valve which 1' s i n turn controlled by' the pressure in a, bleed line connected to the fuel ga's supply andregulated by a'mas'ter pilot valve. In this modification also, Acontinued operation of both regulators requires a maintenance of both the oxygen and the fuel gas supply pressures. Since the pressures are regulated at the torches-iii thi'smodification, it is unnecessary to take into account the pressure drops between the regulators 'and the torches.

In. the accompanying drawings,

Fig. r1 isa cross-sectional view ofA a'pressure regulator 'foran' individual torch constructed in accordance with the present invention.l

Fig; 2 isfanxelevationalView of an oxygen and fuel pressure regulating andjdistributing systemconstructedin accordance with the presetinvention.

Figs-3, 4 and 5 arecross-se'ctional'viewsfof individual pressure regulators which are used inthe system of Fig. 2.

Figg illustrates a' pilot regulator systemfor the control of'oxy'ge'n'and fuelsupplies to 'a number of remotely located individual regulators.

Fig. 7 is a View, partly in section'and partly in elevation, of an individual dual oxygen and fuel pressure regulatorsuitable for use in connection with the pilot regulatorofFig. 6.

Referringjnow VtojFig; l, thereis, shown a'tWo-sta'ge regulatonsuitablefor use inconnection witha'n individual welding or cuttinggoutt in which ajsin'gle tank or grouppf tanks supplies oxygen to a single torch.

Most of the structure of the regulator showny inFig. 1 is conventional, and this conventional structure w'ill first be briefly described. A fluid', such as oxygen, is 'supplied I9 theregulator through anlinlet 1 which communicates with a chamber above a valve 2 operated by a diaphragm 3. Valve 2 is biased to openpostion by a spring 4. The pressure.''in ztcliarnber5- at the utletside of valve 2 acts on diaphragm 3 in a valve closing direction, in oppo- 3 siton to the spring 4. It will be readily understood that the valve 2 and diaphragm 3 cooperate to regulate the pressure in chamber 5, maintaining it at a value determined by the strength of spring 4. Valve 2, diaphragm 3 and spring 4 are the principal parts of the iirst stage of the regulator.

The oxygen ows from chamber 5 through a second valve 6, operated by a second diaphragm 7. A spring 8 biases the diaphragm 7 and valve 6 in a valve opening direction, and is opposed by the pressure in the chamber under the diaphragm 7 and by the pressure in chamber 5 acting on the under side of valve 6. Valve 6, diaphragm 7 and spring 8 are the principal parts of the second stage of the regulator. Oxygen flows from the chamber 10 through an outlet connection 11.

The tension of the spring 8 is determined by the setting of a screw 9. Access to the screw 9 can be had only by removing a cap 9a held in place by a sealed wire 9b. When the cap 9a is sealed in place, the pressure sett'mg of the second stage of the regulator cannot be disturbed Without breaking the seal.

In the regulators of the prior art, a manually operable setting handle was used where the applicant provides the screw 9 under the sealed cap 9a. The other details of construction of the regulator shown in Fig. l are well known, with the exception of the relationships between the areas and pressures set forth below.

As previously pointed out, such regulators are used in connection with oxygen tanks where the absolute inlet pressure to the regulator varies between 150 and 3 kg./cm.2 In such an arrangement, the spring 4 is commonly selected or set to maintain the pressure in chamber 5 at approximately 40 kg./cm.2 When the inlet pressure drops below 40 kg./cm.2, the valve 2 remains open and all the pressure regulation is done by the second stage valve 6. It is possible to maintain a fairly constant outlet pressure over a wide range of rates of iiow, as long as the pressure in chamber 5 remains constant. When the inlet pressure of the regulator drops below the pressure for which the first stage is set, then the pressure in chamber 5 falls, with a resulting drop in the outlet pressure in chamber 10.

In order to study this phenomenon from a mathematical standpoint, let S represent the effective area of the diaphragm 7 exposed to the pressure in the chamber 10 and let s represent the area of the valve 6 exposed to the diiference in pressure between chamber 5 and chamber 10. Let p represent the inlet pressure, p1 the pressure in chamber S and p2 the pressure in chamber 10.

The relation between the areas S and s and the pressure variations Apl and Apz may be expressed as follows:

Apls=Ap2S A172 Mig It has been found by tests that in order to obtain a regulated pressure in the neighborhood of 0.3 to 0.4 kg./cm.2 absolute with a permissible variation of 30 gin/cm.2 over a range of flows from 500 to 20,000 liters per hour, the valve 6 must have a diameter of at least 5 millimeters. The eifective area S in a regulator of suitable dimensions, is approximately 30 square centimeters.

When a conventional regulator is used as described above, the pressure p1 may vary between 40 and 3 kg./cm.2 as the oxygen cylinder is emptied. In such a case, using valve and diaphragm areas as described above, the variation of the outlet pressure p2 would be equal to:

Such a variation of pressure is not permissible in a constant pressure system such as described in the previously mentioned application Serial No. 94,703.

According to the present invention, a modified reguI lator of this type can be used, but the spring 4 must be set or selected to regulate the pressure p1 at a value 01j 4 kga/cm.2 instead of 40.

With such a setting, the variation in p1 as the oxygen cylinder empties is the difference between 4 and 3 kg./cm.2 Hence the variation in the outlet pressure pz becomes:

Such a variation in outlet pressure is permissible in a constant pressure system of the type described. It is, in fact, less than the error in the pressure reading that would be made by a conscientious and able operator using a conventional pressure gauge.

The area of the valve in the second stage regulator may be determined from the known variations in the outlet pressure of the first stage regulator, the desired accuracy of regulation of the second stage outlet pressure, and the area of the second stage diaphragm. In accordance with the following equation, which is derived from the preceding one (assuming that the accuracy is Ap2=0.05p2) summarizing, a pressure regulator of the type described may be utilized to produce a constant outlet pressure with a wide variation in inlet pressure if substantially all the pressure drop is taken in the first stage of the regulator and the unbalanced area of the second stage valve is small with respect to the diaphragm area. A regulator so modified may have its second stage adjustment sealed as described herein, and will supply oxygen or other gas at a substantially constant pressure without attention from the operator. For example, such a regulator has been used to provide an outlet gauge pressure of 300 gm./cm.2, with a variation of only 30 gm./cm.2 over a range of iiows from 500 to 20,000 liters per hour. Furthermore, the regulator is simplified by the elimination of the low pressure gauge and the manual adjustment.

An individual welding or cutting outfit supplied with oxygen by means of a regulator of the type described in Fig. l, can advantageously be equipped with a fuel gas pressure regulator of similar construction. For fuel gases, the pressure regulation problem is more easily solved because the variations in the supply pressure are always much smaller and are sometimes completely absent. For example, liquelied gases, such as propane and butane have substantially constant pressures, determined by the vapor pressure of the liquid. The maximum pressure of acetylene in cylinders is much smaller than that of oxygen, while the pressure variations of acetylene from carbide generators is less than 0.5 kg./cm.2 Many pressure regulators are available which are suitable for use in the fuel gas line, with or without a sealed adjustment as described above.

An arrangement for supplying oxygen from a single tank or group of tanks to a number of cutting or welding torches is described in my copending application Serial No. 649,704, now Patent No. 2,533,729, previously mentioned. In that system, a central pressure regulator is provided which is sufficiently accurate to permit all the required output variations of the various torches connected thereto without disturbing the operation of the other torches, and without requiring any individual adjustment of the pressure at the torches by the torch operators.

There is shown in Fig. 2 an improved pressure regulating apparatus which is suitable for use as the central pressure regulating apparatus in an oxygen and fuel gas distributing system of the type just mentioned. In this arrangement, the operation of both the oxygen and fuel regulators is dependent upon the continuance of the supply pressure of both the oxygen and the fuel. Hence, if either supply pressure fails, the flow of both gases is cut off. With this arrangement, it is unnecessary to provide the check valves or other anti-backiiow devices which have previously been required in oxyacetylene appliances.

Referring now to Fig. 2, there is shown a main acetylene regulator 12 and a main oxygen regulator 13. The details of construction of a regulator such as the regulators 12 and 13 are shown in Fig. 3. Referring briey to Fig. 3, the gas enters by an inlet 14 and passes through a valve 1S connected by a stem 16 to a lever 17. One

arm 18 of the lever 17 bears against a button carried by the icha'mbe'rfsl 1Tline Z'l ahead of tig te' d, dthe othersouree;

pipe '51; 'Siriilarlyjtheioxygeri'reglatr'l'c l by the acetylene pressure in its chamber 21'isuppls`to its outlet pipe 52 oxygentfJXed pressure.

If the pressure of theygel source fails, the pilot regulator Stimmt vsuppl-if= i ,swithexygennd @use v ,iply'pressrefailsthe lator 41 is no' longersup'plied through the bleed e 48;v and the main oxygen regulator vis shut down thereby reducing the pressu'r'einc'ndut 52' substantially simultaneously with the pressure'dr'op in conduit 51.

beiV 21 Qf'regunmr 12 directlyuneicnduif'as.v How-1 ever, such 'an' arrangement" has a'n increased" tendencyr control'lines.' v In supplying oxygen and 'fuel gas to'jweldig or' cutting torches `it l is 'best t ""use' an' ac' 't'ylene pressure'slightlX ting torches have'bceimade"Whichjshow that go'o' re?v r 4 1"is supplied with facetylenelthrough Whih is connecte d to the acetylenesupply mg'fronitheiregulatolf 124 Outlet'49 of, dischargesinto -the chambermZl ofthe main ator 1 2,` and the outlet 5 0 of regulator41' o th; corresponding chamber 21' of the 0'r1 s s s mg briefly, b oth the regulators 401' 'and'. 41L'are. by oxygen; under' pressure regulated 'by the' mast@ `pile regulators@ Regulator 40 'Supplies loro/gen atf'fonsta' `ressur'ejto thechamber 2 1of acetylene `regu- R gulator 41 `"suppli e s acetylene at constant pr oV chamber' 21jof voxygen"regulator `13. Altern thejnlet o f master fpilotregulator 34 c ould bey l conditionjitwillb'e readily'urider pressur'eactn'g on'the' diaphragm in' sprin'gmu'st' decrease as "the 'springexpan'ds Thiscrease-'in 'pressure'ishot large in "welldesign d regulato'sl' Where4 the regulating: apparatus' shown" in" Figf 2 isVA pressure dropl through the' conduits@ 1 and ks2; naybeg considerable, Yparticularlyfat the` higher 'rats ".of'fl Thispressure'drop -can "of course be minimized` `b"y "u' ng;

located atson're distance from 'the torche's'i't 's uppliesftle'i v as'to providef'anfincreasjng discharge pressure vfrom between the lnletjjand outlet `pressures of f reglat veuti'on "the master pilo't'f regulator' 3 4 is constru cted"tto; take'advantage ofthep'ressure Vdecreasing characteristiiT of' l the preliminary 'pressure 'regulator' in' such' a manner;

regulators' i2 and '13 'withincreasig' flow. This'incr the pressuredrop encountered in the lines 50ar1d51V` in such a manner-'as to counteractfthe ,pres'sueldrog in those line's""and`provide 'a substantially Lconstantpresi sure'at"the tor'ch. f, Y.

Referring' 'm the 'pilot reguiator't (`E,.fg.*4)' if' Amaybe` seen that"as"the inlet pressure at 33 decreasesgtheforc; tending'to'close the 'valve 37 decreases,"softhatl'valv@ 3T moves in a'nf opening' direction"`un t il" the decreas ed closin'gj forc'e'on vvalve'37 is balanced by an' increased' closing force' on' diaphragm'SS, d ue'- Y the valve and the increased' outlet that'fop'eningl i,

Let S be the effective area' of'diaphragm 3S `subject,`

tafthel oaelii'ne; off pressure produced vby to thepressure regulated by regulator 34. Letfsr be 'th area Ofivalv 3/which is, .subjectltoithed'ff odeurT at 33"`a'n"d 'Apr'be the permissible variation 'of`but-- let pressure at 38. The relationship between the pressure variations of the two areas defined above may be expressed as:

For example, one conventional regulator, such as that discussed above, when set for a regulated pressure of 2 lig/cm.2 has a variation of approximately 0.3 kg./cm.2 over a range of rates of flow from 500 to 20,000 liters per hour. If the effective area of diaphragm 35 is 15 crn.2 and if a pressure increase of Y0.01 kg/cm.2 is required at the outlet 38 in order to produce a constant pressure at the torches over the desired range of rates of flow, then the area s of the seat against which the valve 37 works must be:

In other words, the seat must have a diameter of 8 mm.

In the modification of the invention just described, the operation of the torches is independent of the variations in the rates of flow of the oxygen and the fuel gas. Furthermore, there is no danger of one of the gases owing backward in the other supply line due to failure of the other source of pressure. In such a system, the hoses connecting the torches to the supply lines may be connected to shut-oit valves of large cross-section located at the ends of the branch supply lines. Individual pressure adjusting and regulating appliances at the torches are not required. Furthermore, anti-backtlow devices at the torches may also be omitted.

Another modification of the present invention is illustrated in Figs. 6 and 7. In this arrangement, the outlet pressures are regulated at each torch by means of a system of pilot lines which connects the gas sources with the several torches, independently of the gas supply lines. These pilot lines distribute a gas at a constant pressure to the torches, where that constant pressure is utilized to control a dual regulator which determines the outlet pressures of both gases. These outlet pressures are entirely independent of any pressure drops in the supply lines. This system may be used where existing supply lines do not fulll the requirements of a centralized pressure control system with regard to pressure drops. It may similarly be used in a new installation in order to permit the use of smaller pipes in long supply lines.

Fig. 6 shows the equipment at the central supply end of the lines. Fig. 7 shows the equipment at one torch. It should be understood that the main acetylene supply line 54 may be connected to several branch acetylene supply lines such as that shown at 82 in Fig. 7. In a similar manner the main oxygen supply line 59 may be connected to several branch oxygen supply lines 83 and the main bleed line 60 of Fig. 6 may be connected to several branch bleed lines 84.

Referring to Fig. 6, there is shown a bleed line 53 connected to the main acetylene supply line 54. A master pilot regulator 55, similar to the pilot regulator 34 of Fig. 4 is connected in the bleed line 53. The pilot regulator S regulates the pressure in its outlet pipe 57, and thereby controls a slave pilot regulator 56 through its outlet pipe 57. Outlet pipe 57 is provided with a xed downstream leak 57a, corresponding to the leak 38a in Fig. 2.

The slave pilot regulator 56 is connected in a bleed line 58 which is supplied from the main oxygen conduit 59. The slave pilot regulator 56 controls the pressure in a pilot line 60. The regulator 56 is similar to the regulators 40 and 41 of Fig. 2, shown in detail in Fig. 5. Since in this system the regulator S5 is not required to compensate for pressure drops between the regulator and the torches, the area of its valve seat should be made as small as possible so as to make it substantially independent of variations in the pressure in the acetylene supply line 54. Regulator 56 is provided with a fixed downstream leak 56a, corresponding to the leak 41a of regulator 41 in Fig. 2.

The pilot tube 60 and its branches 84 supply to each of the several torches oxygen at a ixed pressure. At each torch, this fixed pressure oxygen is supplied to a charnber 69 in a dual regulator shown in Fig. 7.

The pressure in chamber 69 acts on two double diathe flow of oxygen and fuel gas, respectively, are attached to the diaphragms 70 and 71, respectively. The left side of double diaphragm 70 is subject to the regulated oxygen pressure and the right side of double diaphragm 71 is subject to the regulated fuel gas pressure. The valve 61 controls the flow of oxygen to an outlet connection 76 and the valve 62 controls the flow of fuel gas to an outlet connection 77. It will be readily understood that the outlet pressure in the two end chambers of the dual regulator is determined by the control pressure transmitted to its intermediate chamber 69 and in turn determined by the pilot regulators and 56. The fuel gas outlet pressure may conveniently be made slightly larger than the oxygen outlet pressure by making the area of diaphragm 71 subject to the fuel gas outlet pressure smaller than the corresponding area of diaphragm 70 subject to the oxygen outlet pressure, as shown in the drawing.

Two inlet valves 74 and 75 may be connected in the branch supply conduits 83 and 82 ahead of the dual regulator, so that those conduits may be shut olf for purposes of inspection, for example.

In normal operation, the master pilot regulator 55 regulates in accordance with its manual setting the pressure of the fluid supplied to slave pilot regulator 56. The slave pilot regulator 56 in turn regulates the control pressure of the uid supplied through the tube to the compound regulators of the several torches.

If the acetylene supply pressure fails, then the pilot regulator 55 closes, allowing the fluid under pressure in the outlet pipe 57 to How out through the leak 57a. The pressure in pipe 57 therefore falls, and regulator 56 closes under the influence of its biasing spring, allowing the fluid under pressure in the pilot tube 60 to escape through leak 56a. The pressure in tube 60, its branches 84, and the several chambers 69 therefore falls, and the valves 61 and 62 of the several regulators are closed by their respective biasing springs. In a similar manner, if the oxygen supply pressure fails, the oxygen under pressure in tube 60 escapes through leak 56a and the valves 61 and 62 close.

From the foregoing it may be seen that this system provides substantially constant discharge pressure of both the fuel and the oxygen at the torches. Furthermore, the two gases can be supplied at the torches only if both supplies are under pressure. The pressure of both bases at the torches is entirely independent of any pressure drop in the lines supplying them.

I claim:

l. Pressure regulating apparatus for a combustion supporting gas and fuel gas supply system, comprising a combustion supporting gas supply line, a fuel gas supply line, a first bleed line branching from one of said supply lines, a master pilot regulator for regulating the pressure in a portion of said first bleed line, a second bleed line branching from the other supply line, a slave pilot regulator controlled by the regulated pressure in said first bleed line for regulating the pressure in a portion of said second bleed line, a dual regulator connected in the outlet ends of said supply lines for regulating the outlet pressures of the combustion supporting gas and fuel gas, said dual regulator comprising a housing separated into three aligned chambers by two movable walls, each of the end chambers being connected in one of said supply lines and having a valve therein operated by its associated movable wall for regulating the outlet pressure of the gas supplied from its associated supply line, and means for supplying fluid from said second bleed line under the regulated pressure therein to the one of said three chambers between the two movable walls so that the outlet pressures of both the fuel gas and the combustion supporting gas are determined by the pressure in said one chamber.

2. Pressure regulating apparatus for an oxygen and fuel gas supply system, comprising a main oxygen supply line, a main fuel gas supply line, a rst bleed line branching from one of said supply lines, a master pilot regulator for regulating the pressure in a portion of said first bleed line, a second bleed line branching from the other supply line, a slave pilot regulator controlled by the regulated pressure in said first bleed line for regulating the pressure in a portion of said second bleed line, a plurality of pairs of branch supply lines leading from said main supply lines, a plurality of dual regulators,

phragms 70 and 71... Valves 61 and 62 which regulate 85 each connected in the outlet ends of a pair of branch supply lines for regulating the outlet pressures therein, each said dual regulator comprising two outlet pressure chambers each connected in one of its associated branch supply lines and having a movable wall and a valve operated thereby for regulating the outlet pressure of the gas supplied from its associated branch supply line, and ymeans for subjecting the opposite sides of both said movable walls to duid from said second bleed line under the regulated pressure therein so that the regulated outlet pressure of both the fuel gas and the oxygen is determined by the regulated pressure in said second bleed line.

3. Pressure regulating apparatus for a combustion supporting gas and fuel gas supply system, comprising a combustion supporting gas supply line, a fuel gas supply line, a first bleed line branching from one of said supply lines, a master pilot regulator for regulating the pressure in a portion of said first bleed line, a second bleed line branching from the other supply line, a slave pilot regulator controlled by the regulated pressure in said first bleed line for regulating the pressure in a portion of said second bleed line, a dual regulator connected in the outlet ends of said supply lines for regulating the outlet pressures of the combustion supporting gas and fuel gas, said dual regulator comprising two outlet pressure chambers, each connected in one of said supply lines and having a movable wall and a valve operated thereby for regulating the outlet pressure of the gas supplied from its associated supply line, and means for subjecting the opposite sides of both said movable walls to the regulated pressure therein so that the regulated outlet pressures of both the fuel gas and the combustion supporting gas are determined by the regulated pressure in said second bleed line, said movable walls each comprising two spaced diaphragms, means for venting the spaces between the diaphragms to atmosphere, the diaphragm subject to the fuel gas pressure being smaller than the other diaphragms so that the fuel gas outlet pressure is greater than the combustion supporting gas outlet pressure.

4. Pressure regulating apparatus for a combustion supporting gas and a fuel gas supply system, comprising a combustion supporting gas supply line, a fuel gas supply line, a dual regulator for regulating the outlet pressures in the two supply lines, said dual regulator comprising two outlet pressure chambers, each connected in one of said supply lines and having a movable wall and a valve operated thereby for regulating the outlet pressure of the gas delivered from its associated supply line, said movable walls of said pressure chambers being in opposed relation and defining therebetween opposite side walls of a third uid pressure chamber, means for introducing Huid under a control pressure into said third pressure chamber to thereby regulate the pressure of both the fuel gas and the combustion supporting gas in response to variations in said control pressure, and one of said movable walls having a greater area exposed to the pressure of the fluid introduced into said third chamber so that a predetermined differential is maintained between the outlet pressures of the two supply lines.

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